Nonnative fishes represent a significant impediment to the recovery of imperiled fishes, including those endemic to the Colorado River in the southwestern United States. Efforts to control nonindigenous fish abundance in the upper Colorado River basin have been unsuccessful owing in part to lack of knowledge regarding nonnative fish recruitment sources. We determined the source habitat (floodplain pond versus riverine habitats) for nonnative centrarchid fishes (largemouth bass Micropterus salmoides, green sunfish Lepomis cyanellus, bluegill L. macrochirus, and black crappie Pomoxis nigromaculatus) in the upper Colorado River using stable hydrogen isotopic composition (δD) and strontium: Calcium (Sr: Ca) ratios in fish otoliths as natural markers of environmental history. Stable hydrogen isotope analysis revealed that 59% of centrarchids exhibited the otolith core signatures expected for riverine‐origin fish, while 22% had emigrated from floodplain ponds and 19% were of uncertain origin. Strontium: Calcium ratio data were consistent with the δD assays and indicated that relatively few fish immigrated to the river from high‐salinity habitats. Black crappie was the only species that originated primarily from floodplain ponds. Efforts to control the abundance of most of the fishes included in this study should be concentrated in riverine habitats given the hydrologic conditions (below‐average river discharge) present during our study. However, the proportion of pond‐origin fish increased with fish age, which, coupled with historical river discharge data, suggested that floodplain pond contributions to riverine nonnative fish populations fluctuate with the interannual variations in flow regime and river‐pond connectivity. Our results are the first to demonstrate the utility of δD as a natural marker of fish environmental history that will probably provide valuable insights into the management of fish in other environments.

Cultured metalarvae and mesolarvae of brook trout Salvelinus fontinalis, brown trout Salmo trutta, rainbow trout Salmo gairdneri, and cutthroat trout Salmo clarki were analyzed for distinguishing pigmentation patterns, variation in size and abundance of oil globules in the yolk, and differences in 48 morphometric and meristic characters by comparison of percent standard lengths and multivariate statistical techniques. Rainbow and cutthroat trouts differed from each other only in that the insertion of the dorsal fin and origin of the adipose fin were more posterior in rainbow trout. Brown trout differed from the other species in having longer pectoral fins, an elliptical yolk and unique pigmentation on the lower jaw, caudal fin, and adipose fin. Brook trout differed from the other species by having numerous minute oil globules in the yolk; a distinctively longer adipose fin; prominent pigmentation on the anterior margin of the mandible, caudal fin, and adipose fin; and a greater number of dorsal and ventral parr marks. Brown and brook trout metalarvae had unilobed preanal finfolds, whereas rainbow and cutthroat trout metalarvae had bilobed preanal finfolds. Each of the species was clustered into a distinct group by discriminantfunction analysis, but principal-component analysis was inadequate for complete separation of these species. Larva stages of widely distributed and cultured salmonids such as brook trout Salvelinus fontinalis, brown trout Salmo trutta, and rainbow trout Salmo gairdneri have been described (Crawford 1925; Wales 1941; Knight 1963; Ballard 1973; Lister 1980), but these descriptions are largely incomplete and inadequate for identification purposes. Perhaps the most useful criteria described to date for distinguishing brook, brown, and rainbow trout larvae and juveniles were provided by Bacon (1954), Weisel (1966), Marcinko (1978), and Balon (1980). Larvae of cutthroat trout Salmo clarki are very similar to, and especially difficult to distinguish from, those of the closely related rainbow trout. The objectives of this investigation were to provide detailed comparative descriptions of the aforementioned trout larvae, verify diagnostic characters suggested by previous investigators, and determine additional (and perhaps more obvious and consistent) differences for identification purposes. Emphasis has been placed on external pigmentation, size and abundance of oil globules in the yolk, and morphology (in-cluding numerous morphometric and meristic characters). Methods Approximately 50 hatchery-and laboratoryreared specimens of each of the four species, from recently hatched to early juvenile stages, were examined. All were obtained between 1976 and 1982. The brook, brown, and cutthroat trout series were raised at approximately 12 C from fertilization or an eyed developmental stage, and the rainbow trout series was raised at 15-17 C from an eyed-egg stage. The brown and cutthroat (greenback subspecies S.c. stomias) trout originated from Colorado brood stock in Delaney Butte Lake and Island Lake, res...

The Wadena City Health Study was undertaken to assess the nature of type II (non-insulin-dependent) diabetes and its relationship to aging. This article reports the study methodology and prevalence estimates for type II diabetes and impaired glucose tolerance (IGT) for the adult population of Wadena, Minnesota. The sampling frame for the study included all known diabetic individuals and all other residents based on a complete citywide census of residents greater than or equal to 20yr of age. A stratified random sample that included three stratifying factors (age [20-39, 40-59, greater than or equal to 60 yr], sex, and self-reported weekly use of any prescribed medication was drawn from the other residents). The study protocol required diet preparation and two full mornings of testing. Data collected included height, weight, and blood pressure measurements and both a personal interview and a medications questionnaire. A 75-g oral glucose tolerance test (OGTT) and a test with a standard liquid meal (Ensure-Plus challenge test [EPCT], Ross) were done on two mornings, with the order of testing randomly assigned. Clinical tests included one-time samples for hemoglobin, glycosylated hemoglobin, plasma cholesterol, triglycerides, and lipoproteins. Blood samples for glucose and creatinine assays were taken during the OGTT; blood samples for glucose, free fatty acid, creatinine, and C-peptide were taken during the EPCT. Urine collections were performed for both challenge tests and assayed for C-peptide and creatinine. Seventy-one percent of the known diabetic subjects, and 65% of the stratified random sample participated in the study.(ABSTRACT TRUNCATED AT 250 WORDS)